The present invention relates to a method for a vehicle, in particular to a method for providing an on-board model used to determine faults in a part of a vehicle, such as an internal combustion engine. Further, the present invention relates to a method for determining faults in a vehicle being provided with such on board model.
Heavy vehicles such as trucks, construction vehicles, etc. are usually driven by an internal combustion engine (ICE). The ICE is typically a diesel engine provided with one or more turbochargers. Trucks are normally operated under extreme conditions, such as long distances and long driving periods. Once the vehicle is subject to a fault requiring service or maintenance the cost for the truck owner is rapidly increasing. Hence, in many cases it is desirable to detect faults early, preferably before such faults causes unplanned downtime of the vehicle.
For this, model based approaches have been suggested. Typically such approaches require a model representing specific parts of the vehicle, e.g. the turbocharger. The model requires one or more inputs corresponding to actual driving parameters, and delivers one or more outputs. Said outputs are compared with actual parameter values obtained during driving, and a match between the actual parameter values and said outputs indicates that the specific part of the vehicle is functioning properly. Correspondingly, a deviation between the actual parameter values and the outputs indicates a malfunction.
Another method is described in US20120290190. This document describes a method for diagnosing an exhaust gas recovery (EGR) system. The measured or actual EGR gas temperature is compared to an EGR gas temperature that has been empirically determined and stored in a table or function in a memory of a controller. If the actual EGR temperature is less than or greater than the empirically determined EGR gas temperature by more than a predetermined amount, EGR system degradation based on EGR gas temperature may be determined and recorded to memory.
Although there are currently proposed methods providing fault detection in vehicles, it has been proven to be very difficult to provide a sufficiently accurate and reliable method in these applications. First of all, a vehicle is a very complex construction with a vast amount of critical machine parts of which proper functioning is critical for the overall vehicle performance. This particularly applies to the engine, as well as to associated parts such as the exhaust gas flow path. Secondly, the resources for performing such methods on board are very limited, both in terms of available memory as well as processing power.
In view of these limitations there is need for other methods for allowing fault detection in vehicles. More particularly there is a need for improved methods allowing various faults to be detected on board the vehicle, as well as methods which are easy to expand to further parts of vehicle, thus allowing the detection of various faults also in such additional parts.
Accordingly, it is desirable to mitigate or eliminate the above-identified deficiencies in the art and disadvantages singly or in any combination.
An idea of an aspect of the invention is to provide a model for a part of a vehicle, such as an internal combustion engine, wherein a specific operation state is simulated for one or more fault types thus resulting in one or more simulations, and wherein each simulation is stored as a representation of one or more operating parameter values.
A yet further idea of the invention is to store such representations in a vehicle, and use such representations for comparing the stored operating parameter values with measured values during vehicle operation. By performing such comparison for each one of the representations, i.e. for the different fault types, it is possible to determine which fault type is most likely to be present.
According to a first aspect of the invention a method for providing a model for a part of a vehicle is provided. The method comprises the steps of selecting at least one operation state; selecting at least one possible fault type for said vehicle part; simulating vehicle part performance for said at least one operation state during the occurrence of said at least one possible fault type; for each simulation creating a representation of said vehicle part performance in which each representation is associated with at least one operating parameter value; and storing said at least one representation.
The method may further comprise the steps of simulating vehicle part performance for said at least one operation state with no fault type occurring; and for said simulation with no fault type occurring creating a representation of said vehicle part performance in which said representation is associated with at least one operating parameter value. Hence, the model also includes representations for a fault-free vehicle part.
Said operation state may correspond to a specific driving characteristics for a specific surrounding condition, and said fault type may correspond to a specific fault with a specific magnitude.
The step of simulating vehicle part performance may be performed for each one of said at least one operation state during the occurrence of each one of said at least one possible fault type, resulting in a set of unique simulations.
Further, said vehicle part may be an internal combustion engine, or parts thereof, and wherein each one of said representations is a series of operating parameter values for a specific output torque, a specific engine speed, a specific ambient condition, and a specific fault type.
In an embodiment, said vehicle part may be an internal combustion engine, and said at least one operating parameter may be selected from the group consisting of: turbocharger boost pressure, turbocharger inlet pressure, turbocharger speed, turbocharger outlet temperature, turbocharger inlet temperature, and/or exhaust gas recovery temperature.
According to a second aspect, an electronic control unit is provided. The electronic control unit has a memory storing a model according to the first aspect.
According to a third aspect, a method for identifying faults of a part of a vehicle during operation is provided. The method comprises the steps of determining an actual operation state of said vehicle part; receiving a value of at least one operating parameter from each one of a plurality of stored representations, which correspond to said determined operation state for different fault types, for which each one of said representations is associated with at least one operating parameter value; detecting at least one actual value of said at least one operating parameter; and identifying a specific fault type associated to a specific representation for which the at least one received operating parameter value is most similar to said detected actual operating parameter value.
The step of identifying a specific fault type may further comprise computing residuals between the received operating parameter values and the detected actual operating parameter values for each one of said representations; selecting one representation for which said residuals have a minimum variance; and identifying a specific fault type associated with the selected representation.
Further, the step of detecting at least one operating parameter value may be repeated for detecting a series of actual values for said at least one operating parameter.
According to a fourth aspect, a computer program product is provided. The computer program product comprises program code means stored on a computer readable medium for performing all steps of the method according to the third aspect when said program product is run on a computer.